This only makes sense if you have few thousands orphan miles on some family account that would never be used and you are not able to top that account for a reasonable award. Otherwise this is just waste of money.

Here are the terms and conditions of the AA offer:

AAdvantage members must complete a share transaction beginning 7:00 am CT December 15, 2014, to 11:00 pm CT December 30, 2014 to be eligible for a 30% discount. Discount applies to the mileage transfer cost and does not apply toward the $20 transaction processing charge. AAdvantage accounts less than 14 days old are not permitted to Share miles. The miles transferred with the Share Miles program do not count towards AAdvantage Gold, AAdvantage Platinum, AAdvantage Executive Platinum or AAdvantage Million MilerSM status qualification. A confirmation email will be sent to the primary Sharer and recipient using the email address associated with the AAdvantage account and any additional email address provided.